This invention relates to the preparation of semiconductor device structures. Particularly, the present invention pertains to methods of forming substantially carbon-free, and, optionally, oxygen-free, conductive layers using an organometallic catalyst.
Chemical vapor deposition (hereinafter xe2x80x9cCVDxe2x80x9d) is defined as the formation of a non-volatile solid layer or film on a substrate by the reaction of vapor phase reactants that contain desired components. The vapors are introduced into a reactor vessel or chamber, and decompose and/or react at a heated surface on a wafer to form the desired layer. CVD is but one process of forming relatively thin layers on semiconductor wafers, such as layers of elemental metals or compounds. It is a favored layer formation process primarily because of its ability to provide highly conformal layers even within deep contacts and other openings.
For example, a compound, typically a heat decomposable volatile compound (also known as a precursor), is delivered to a substrate surface in the vapor phase. The precursor is contacted with a surface which has been heated to a temperature above the decomposition temperature of the precursor. A coating or layer forms on the surface. The layer generally contains a metal, metalloid, alloy, or mixtures thereof, depending upon the type of precursor and deposition conditions employed.
Precursors typically utilized in CVD are generally organometallic compounds, wherein a hydrocarbon portion of the precursor functions as the carrier for the metal or metalloid portion of the precursor during vaporization of the liquid precursor. For microelectronic applications, it is often desirable to deposit layers having high conductivity, which generally means that the layers should contain minimal carbon and oxygen contaminants. However, one problem of a CVD deposited layer formed from an organometallic precursor is incorporation of residual carbon from the hydrocarbon portion of the precursor and oxygen that may be present in the atmosphere during deposition. For example, oxygen incorporation into the layer before or after deposition generally results in higher resistivity. Further, it is also believed that organic incorporation (such as pure carbon or hydrocarbon) into the resultant layer reduces density and conductivity. A low density layer can subsequently lead to oxygen incorporation into the layer when it is exposed to ambient air.
Conductive layers formed by CVD processing can be used in the fabrication of various integrated circuits. For example, capacitors are the basic energy storage components in storage cells of memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and even in ferroelectric memory (FE) devices. As memory devices become more dense, it is necessary to decrease the size of circuit components. One way to retain storage capacity of memory devices and decrease its size is to increase the dielectric constant of the dielectric layer of the capacitor component. Such components typically consist of two conductive electrodes insulated from each other by a dielectric material. In order to retain storage capacity and to decrease the size of memory devices, materials having a relatively high dielectric constant can be used as the dielectric layer of a storage cell. Materials having relatively high dielectric constants are generally formed on a device surface as thin layers. Generally, high quality thin layers of metals and conductive metal oxides, nitrides, and silicides, are used as electrode materials for storage cell capacitors. To be effective electrodes, low resistivity is desired. Therefore, layers having low carbon and/or oxygen content are desired. Further, various applications also require such low resistivity conductive layers, e.g., contacts, interconnects, etc. In addition, the presence of carbon in an electrode layer may xe2x80x9cpoisonxe2x80x9d the dielectric layer thus, reducing the effectiveness of the capacitor.
Thus, what is yet needed are methods for forming substantially carbon- and oxygen-free conductive layers useful for semiconductor structures, that can be used in microelectronic devices, such as memory devices. For example, a substantially carbon- and oxygen-free layer is desirable when a conductive material, e.g., ruthenium, is used as a conductive layer. In general, such a conductive layer preferably contains unoxidized or relatively minor amounts of oxidized metal or metalloid which, in large amounts, can adversely affect its characteristics. Further, conductive layers containing relatively large amounts of carbon and/or oxygen do not provide adequate conductivity characteristics.
Advantageously, the present invention provides a method for forming a substantially carbon-free and, optionally, oxygen-free layer including a metal- or metalloid containing material. Preferably, a method according to the present invention includes forming a layer in the presence of an organometallic catalyst. The present invention also provides a substantially carbon-free and, optionally, a substantially oxygen-free conductive layer that can be used as a barrier layer, and/or an adhesion layer, on an electrode, or any other conductive layer in an integrated circuit structure, such as in a capacitor of a memory device.
A method according to the present invention is particularly well suited for forming layers on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. It is to be understood that a method according to the present invention is not to be limited to layer formation on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. A method according to the present invention can also be used in silicon-on-insulator technology. The layers can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers herein to a base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon or sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers herein to a semiconductor substrate or a substrate having one or more layers or structures formed thereon.
Accordingly, one aspect of the present invention provides a method for use in fabrication of integrated circuits. Preferably, the method includes the steps of forming a substrate assembly having a surface and forming a substantially carbon- and oxygen-free layer from a precursor comprising a conductive material in an oxidizing atmosphere and in the presence of an organometallic catalyst. A metal portion of the organometallic catalyst is preferably different than the conductive material of the precursor.
As used herein, xe2x80x9csubstantially carbon-freexe2x80x9d refers to an amount of carbon present in a layer that is preferably about 1.0% by atomic percent or less, more preferably about 0.1% by atomic percent or less, and most preferably about 0.05% by atomic percent or less. If used, xe2x80x9csubstantially oxygen-freexe2x80x9d refers to an amount of oxygen present in a layer that is preferably about 1.0% by atomic or less, more preferably about 0.5% by atomic or less, and most preferably about 0.1% by atomic or less.
Preferably, the metal portion of the organometallic catalyst is selected from the group consisting essentially of platinum, paladium, rhodium, and iridium and the material is selected from the group consisting essentially of a metal, a metalloid, and mixtures thereof. The metal and the metalloid can each be in the form of a sulfide, a selenide, a telluride, a nitride, a silicide, an oxide, and mixtures thereof. The material is preferably selected from the group consisting essentially of titanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel, iridium, cerium, tungsten, aluminum, copper, and mixtures thereof.
Additionally, the method of the present invention provides that the substantially carbon- and oxygen-free layer can further include a metal selected from the group consisting essentially of platinum, paladium, rhodium, and iridium. Preferably, the metal portion from the organometallic catalyst included in the substantially carbon- and oxygen-free layer is in an amount no greater than about 20% by atomic percent.
Preferably, the step of forming the substantially carbon- and oxygen-free conductive layer includes depositing a precursor by chemical vapor deposition in the presence of a platinum-containing organometallic catalyst. More preferably, the precursor includes a material selected from the group consisting essentially of titanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel, iridium, cerium, tungsten, aluminum, copper, and mixtures thereof.
Another aspect of the present invention provides a method for use in formation of a capacitor. Preferably, the method includes the steps of forming a surface of a substrate assembly and forming a first electrode on at least a portion of the surface of the substrate assembly. Preferably, the first electrode includes a substantially carbon- and oxygen-free layer deposited in an oxidizing atmosphere in the presence of an organometallic catalyst, wherein the substantially carbon- and oxygen-free layer is formed from a conductive metal-containing precursor, wherein the conductive metal of the precursor is not the same as a metal portion of the organometallic catalyst. The method also includes the steps of forming a dielectric material over at least a portion of the first electrode; and forming a second electrode on at least a portion of the dielectric material.
Preferably, the step of forming the substantially carbon- and oxygen-free conductive layer includes forming a substantially carbon- and oxygen-free layer by chemical vapor deposition. The substantially carbon- and oxygen-free conductive layer may also be a substantially carbon- and oxygen-free conductive barrier layer.
Yet another aspect of the present invention provides a semiconductor structure. Typically, the semiconductor structure includes a substrate assembly including a surface and a substantially carbon- and oxygen-free conductive layer comprising a major portion of a conductive material and a minor portion of a metal selected from the group consisting essentially of platinum, paladium, rhodium, and iridium, wherein the major portion of the conductive material is not the same as the minor portion of the metal. Preferably, the minor portion comprises about 20% by atomic percent or less of the substantially carbon- and oxygen-free conductive layer.
The substantially carbon- and oxygen-free conductive layer preferably includes a material selected from the group consisting essentially of titanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel, iridium, cerium, tungsten, aluminum, copper, and mixtures thereof. Thus, in the semiconductor structure of the present invention, the substantially carbon- and oxygen-free conductive layer may be at least one of a semiconductor structure selected from the group consisting essentially of an electrode layer, an electrode, a barrier layer, a contact layer, an interconnect component, and an adhesion layer.
A further aspect of the present invention provides a semiconductor structure that typically includes a substrate assembly including a surface and a substantially carbon-free conductive layer comprising a major portion of a conductive metal oxide and a minor platinum portion. Preferably, the minor platinum portion comprises about 20% by atomic percent or less of platinum in the substantially carbon-free conductive layer.
The substantially carbon- free conductive layer may include a major portion of a metal oxide selected from the group consisting essentially of aluminum oxide, titanium oxide, tungsten oxide, ruthenium oxide, osmium oxide, iridium oxide, rhodium oxide, tantalum oxide, cobalt oxide, copper oxide, and mixtures thereof.
Yet a further aspect of the present invention provides a memory cell structure including a substrate assembly including at least one active device and a capacitor formed relative to the at least one active device. The capacitor comprises at least one electrode including a substantially carbon- and oxygen-free conductive layer, wherein the substantially carbon- and oxygen-free conductive layer comprises a major portion of a conductive material selected from the group consisting essentially of titanium, tantalum, ruthenium, osmium, iron, rhodium, cobalt, nickel, iridium, cerium, tungsten, aluminum, copper, and mixtures thereof; and a minor portion of a metal selected from the group consisting essentially of platinum and paladium.
The capacitor may further include a first electrode formed on a silicon-containing region of the at least one active device; a dielectric material on at least a portion of the first electrode; and a second electrode on the high dielectric material, wherein the first electrode comprises the substantially carbon- and oxygen-free conductive layer. The substantially carbon- and oxygen-free conductive layer may be at least one of a semiconductor structure selected from the group consisting essentially of an electrode layer, an electrode, a barrier layer, a contact layer, an interconnect component, and a bond pad.
Another aspect of the present invention provides a method for forming a substantially carbon- and oxygen-free conductive layer. Preferably, the method includes forming a substrate assembly including a heated surface; forming a reactor chamber having an oxidizing atmosphere within the chamber; supplying a precursor to the reactor; and supplying an organometallic catalyst to the reactor. Preferably, the substantially carbon- and oxygen-free conductive layer forms on the heated surface. The oxidizing atmosphere may include a compound selected from the group consisting essentially of oxygen, ozone, nitrous oxide, hydrogen peroxide, R2O2, and a combination thereof, wherein R is selected from the group consisting of a saturated or unsaturated linear, branched or cyclic hydrocarbon group having about 1 carbon atom to about 20 carbon atoms, preferably about 2 carbon atoms to about 12 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, heptyl, dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. Preferably, the reaction chamber is at a pressure of about 0.5 torr to about 50 torr.
The method of the present invention may also include the step of supplying a reactive gas to the reactor, wherein the reactive gas is selected from the group consisting essentially of nitrogen-containing gases, silane, hydrogen sulfide, and mixtures thereof.
Another aspect of the present invention provides a method of optimizing components in a conductive layer. Preferably, the method includes the step of forming a conductive layer, wherein forming the conductive layer includes forming a reactor chamber having a known concentration of oxygen in an oxidizing atmosphere; forming a substrate having a heated surface; supplying a fixed amount of a precursor to a reactor; and supplying a fixed amount of an organometallic catalyst to the reactor. The method also includes the step of analyzing the conductive layer for component amounts. The steps of forming and analyzing a conductive layer can be repeated, wherein one of the fixed amount of the organometallic catalyst or the concentration of oxygen in the oxidizing atmosphere is varied until carbon is detected in the conductive layer.
Preferably, the fixed amount of the organometallic catalyst is about 15% by atomic percent and is varied by decreasing the fixed amount. Additionally, and preferably, the known concentration of oxygen in the oxidizing atmosphere is about 30% by atomic percent and is varied by decreasing the known amount. The amount of organometallic catalyst can be optimized empirically such that the amount of catalyst can be reduced until carbon is detected in the layer formed.